Optical imaging techniques have been widely used in a number of important biomedical applications, but they face a serious challenge for deep tissue imaging due to the difficulty of recovery of scattered photons in turbid media. Photoacoustic tomography (PAT), which is based on a hybrid technology that combines rich optical contrast mechanisms and superior ultrasonic penetration depth and resolution, has been demonstrated to successfully address the challenge in conventional optical imaging. Although some basic ideas used for image reconstruction in conventional imaging modalities, such as in computed tomography (CT), may be taken for PAT, significant effort is necessary for adopting those image reconstruction approaches to achieve optimized PAT images due to its unique data acquisition.